1. Field of the Invention
This invention relates to an improved support for pivoting a frame about an axis of pivotation by the use of multiple linear bearing surfaces.
2. Description of the Prior Art
There are numerous schemes and designs for supporting pivoting structures, ranging from simple ball or journal bearings and upward in complexity. Where it is possible to attach support members to a pivoting member at any of many support points, no problem of weight distribution arises. However, major problems arise where there are limited support points as for instance where rolling surfaces are involved, or where the weight for a support member requires that support devices be attached at remote points.
An example of such problems can be found in applications where webbed material is handled over a plurality of rollers, such as for a paper web in a printing operation, or in the manufacture and processing of textiles and carpets. Often it is necessary to pass webs over and through a number of rollers, threading, turning, wrapping and in many other ways contacting rollers that often have large cantilevered forces upon their end bearing supports. Furthermore, rollers used in such applications often must be supported in a variety of positional modes, thereby requiring vertical, overhead or other unusual support structure and specially positioned bearing surfaces.
In utilizing rollers of the kind mentioned, it is sometimes necessary that a web be pivoted about a selected axis so as to correct the web's direction of travel due to deviations in the web's path of travel. An apparatus for supporting and correcting web travel deviations utilizing two linear support positions was taught in U.S. Pat. No. 2,797,091, issued to I. L. Fife. The apparatus of that patent has found many commercial applications, but its uses have been restricted because of the limited bearing surface available.
Others have sought to complement or extend the utilization range of linear bearings for pivoting structure by introducing curvilinear support posts. The obvious advantage of curved posts has been the ability to pivot a frame or a structural member while maintaining better weight and force distribution. Of course, the utilization of curvilinear bearing posts presents the problem of bearing attachment to the posts where large bearings are utilized, limiting the dimensions that can be used for such bearings. That is, a large bearing block requires precision matched curved surfaces for the block and the post, or a restriction to the utilization of very gradually curving surfaces. Either of these restrictions severely limits the radius of turn available for the pivoting structure. Another problem presented by the use of curvilinear bearing posts is that control mechanisms must be especially adapted for the curvilinear design.
While the discussion to this point has largely dealt with supporting pivoting rollers, the problem solved by the present invention by no means is so restricted. There is a need in numerous instances for the support of a frame or structural member on multiple linear bearings that permit good pivoting characteristics while providing even weight and force distribution on the bearings. It is to that requirement that the present invention is directed.